Structures within the Valhalla impact basin on Jupiterís moon Callisto

Fig. 9.26 . This mosaic of two images shows an area within the Valhalla region on Jupiterís outermost large moon, Callisto. Numerous impact craters, ranging in size from 155 meters to 2.5 kilometers across, are seen in the mosaic, which is approximately 33 kilometers wide. There is an unexpected absence of small craters and the ragged rims of the existing craters suggest an erosion process, which is believed to be due to sublimation of volatiles from the surface ice. A prominent, dark fault scarp, or cliff, and smaller parallel ridges are also pictured (top right). These images were obtained on 4 November 1996 from the Galileo spacecraft. (Courtesy of NASA/JPL/ASU.)